The fluorinated lithiumalkoxide LiORF (RF = C(CF 3)2Mes), the alcohol RFOH and Attempts to use them as precursors for new weakly coordinating anions (WCAs)

Article abstract of DOI:10.1002/zaac.200700593

The Li alkoxides [LiOR^F]₄ (1), [LiOR ^F]₄[LiF]₂ (2) and the solvent coordinated Li-gallate Li(C₂H₄Cl₂)[Ga(OR^F) ₂(Br)₂] (R^F = C(CF₃)₂Mes) (3) were prepared by reacting a stoichiometric amount of Mes-Li · OEt₂ and gaseous (CF₃)₂CO giving 1. Subsequently, 2 was formed in 28 % yield in a poorly understood sequence by addition of AlBr₃ to 1. Upon addition of GaBr₃ to four equivalents of 1 compound 3 formed. The Li alkoxide 1 forms a puckered eight membered (Li-O)₄ ring and compound 2 forms an almost ideal double heterocubane with a complexed Li₂F₂ four membered ring in the center. The Li-gallate 3 contains the tetrahedral anion [Br ₂Ga(OR^F)₂]^- and coordinates a Li(Cl₂C₂H₄)⁺ cation by two contacts to the oxygen atoms of the alkoxide. The latter describes the first account of a Li-chloroalkane complex. 1 to 3 were characterized by multinuclear NMR, IR and Raman spectroscopy as well as by their single-crystal X-ray structures. It appears that the steric bulk of the OR^F alkoxide is too large to allow for the desired synthesis of the weakly coordinating anions [M(OR ^F)₄]^- (M = Al, Ga). In agreement with this, the also prepared new fluorinated alcohol HO-R^F did neither react with LiAlH₄ (various solvents) nor could electrochemically be reduced with H₂ formation (CV).

Full text of DOI:10.1002/zaac.200700593

DOI: 10.1002/zaac.200700593
The Fluorinated Lithiumalkoxide LiORF (RF ؍ C(CF3)2Mes), the Alcohol
RFOH and Attempts to use them as Precursors for New Weakly Coordinating
Anions (WCAs)
Lutz O. Müllera, Rosario Scopelittib, and Ingo Krossinga,*
a Freiburg/Germany, Institut für Anorganische und Analytische Chemie der Universität
b
´
Lausanne/Switzerland, Institut des Sciences et Ingenerie Chimiques
Received October 15th, 2007; accepted January 15th, 2008.
Abstract. The Li alkoxides [LiORF]4 (1), [LiORF]4[LiF]2 (2) and the
describes the first account of a Li-chloroalkane complex. 1 to 3
were characterized by multinuclear NMR, IR and Raman spec-
troscopy as well as by their single-crystal X-ray structures. It ap-
pears that the steric bulk of the ORF alkoxide is too large to allow
for the desired synthesis of the weakly coordinating anions
[M(ORF)4]Ϫ (M ϭ Al, Ga). In agreement with this, the also
prepared new fluorinated alcohol HOϪRF did neither react with
LiAlH4 (various solvents) nor could electrochemically be reduced
with H2 formation (CV).
solvent coordinated Li-gallate Li(C2H4Cl2)[Ga(ORF)2(Br)2] (RF
ϭ
C(CF3)2Mes) (3) were prepared by reacting a stoichiometric
amount of Mes-Li·OEt2 and gaseous (CF3)2CO giving 1. Sub-
sequently, 2 was formed in 28 % yield in a poorly understood se-
quence by addition of AlBr3 to 1. Upon addition of GaBr3 to four
equivalents of 1 compound 3 formed. The Li alkoxide 1 forms a
puckered eight membered (LiϪO)4 ring and compound 2 forms
an almost ideal double heterocubane with a complexed Li2F2 four
membered ring in the center. The Li-gallate 3 contains the tetra-
hedral anion [Br2Ga(ORF)2]Ϫ and coordinates a Li(Cl2C2H4)ϩ cat-
ion by two contacts to the oxygen atoms of the alkoxide. The latter
Keywords: Li alkoxide; Heterocubane; Crystal structures; Alumi-
num; Weakly coordinating anion (WCA)
Introduction
Such weakly coordinated Liϩ ions may even be soluble in
toluene [12] and n-hexane [13] and are therefore active as
catalyst in organic transformations as Diels-Alder reactions,
1,4-conjungated additions and pericyclic arrangement reac-
tions [12, 13]. The related Li[Al(OC(CF3)2Ph)4] was shown
to be a good catalyst for this purposes [13].
The most widespread synthesis [3] of Li-alkoxides LiOR
is the reaction of the alkaline metals or alkaline metal
hydrides with alcohols RϪOH (R ϭ organic). Due to the
small and polarizing Liϩ ion, the structures tend to be ag-
gregated LiϩXϪ (X ϭ halide, OR, NR2): Monomeric ion
pairs of LiϩXϪ only exist in the gasphase (X ϭ halide [14],
NR2 [15]), which associate in condensed phases Ϫ as ligand
free systems Ϫ with formation of ring molecules (LiX)n
(n ϭ 2, 3 rarely 4 (types I, II, III), infinite chains (LiX)ϱ
(type IV), heterocubanes (CNLi ϭ 3) (see type V), aggre-
gated heterocubanes (type VI), ladders (type VII) or even
hexagonal prisms (type VIII in Fig. 1).
It has been reported that Li-containing complexes aggre-
gate yielding ϳ12 general structural types [1Ϫ7]. The fac-
tors that determine the final structure of these Li species
have been attributed to the choice of solvent (Lewis ba-
sicity) used during their synthesis, the electron-donating
ability of the α-atom of the ligand (C, N, O or X), the bond-
ing ability of the ligand (mono-, bi-, tri-, or polydentate),
or the steric bulk and number of the ligands (ϪX, ϪOR,
ϪNR2) [1Ϫ8].
We are interested in fluorinated metal alkoxides [9, 10] as
precursors to new weakly coordinating anions (WCAs) in
alkoxy metalates [M(ORF)4]Ϫ [11] to complement our
presently used (per-)fluorinated alkoxy residues ORF
ϭ
C(CF3)3, C(CF3)2R (R
OC(CF3)2Mes (Mes
ϭ
H, Me) with the bulky
2,4,6-Me3C6H2). The desired
ϭ
[Al(ORF)4]Ϫ WCA with RF ϭ C(CF3)2Mes appeared a
valuable synthetic goal, since it should be very stable
towards electrophilic attack due to the steric shielding pro-
vided by the bulky OC(CF3)2Mes ligand. Moreover, WCAs
such as those in the aluminate Li[Al(ORF)4] [11] evoke
easily accessible Liϩ cations, which tend to be “naked“.
Herein we report on the preparation and structural
characterization of compounds containing the ORF residue
(RF ϭ C(CF3)2Mes), i.e. structural variations of LiORF, the
alcohol HOϪRF and first attempts to use the alkoxide/
alcohol for the preparation of WCAs of type [M(ORF)4]Ϫ
(M ϭ Al, Ga) by reaction with MBr3/LiMH4.
* Prof. Dr. I. Krossing
Institut für Anorganische und Analytische Chemie
Albert-Ludwigs-Universität Freiburg
Albertstr. 21
D-79104 Freiburg/Germany
E-mail: krossing@uni-freiburg.de
Tel.: ϩ49-761-2036121
Results and Discussion
Syntheses
Preparation of [LiOC(CF3)2Mes]4 (1): 1 was formed by the
reaction of MesϪLi·OEt2 and gaseous (CF3)2CO (Eq. (1)).
Fax: ϩ49-761-2036001
Z. Anorg. Allg. Chem. 2008, 634, 1035Ϫ1040
© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
1035

L. O. Müller, R. Scopelitti, I. Krossing
Figure 2 Molecular structure of [LiOC(CF3)2Mes]4 (1) at 140 K
with thermal displacement ellipsoids showing 50 % probability.
˚
Selected bond lengths and interactions are given in A and angles in °:
Li(1)ϪO(1) 1.802(9), Li(1)ϪO(2) 1.821(9), Li(1)ϪC(1) 2.744(10),
Li(1)ϪC(13) 2.681(10), Li(1)ϪC(16) 2.791, Li(1)ϪC(21) 2.597(9),
Li(2)ϪO(1)Ј 1.857(9), Li(2)ϪO(2) 1.852(8), O(1)ϪC(1) 1.364(5), C(1)ϪC(4)
1.567(6), O(2)ϪC(13) 1.361(5), C(13)ϪC(14) 1.561(7), C(13)ϪC(15)
1.546(7), C(13)ϪC(16) 1.562(6), Li(2)ϪF(2)Ј 2.123(9), Li(2)ϪF(4)Ј
2.261(10), Li(2)ϪF(10)Ј 2.787(1), Li(2)ϪF(8)Ј 2.155(10), (CϪF)av. 1.331(7);
O(1)ϪLi(1)ϪO(2) 138.2(5), Li(1)ϪO(1)ϪLi(2)Ј 121.1(4), Li(1)ϪO(2)ϪLi(2)
115.7(4), O(2)ϪLi(2)ϪO(1)Ј 127.3(5), C(1)ϪO(1)ϪLi(1) 119.5(4),
C(13)ϪO(2)ϪLi(1) 114.0(4), O(1)ϪC(1)ϪC(3) 109.3(3), O(1)ϪC(1)ϪC(4)
112.0(4), C(3)ϪC(1)ϪC(4) 108.1(4), O(2)ϪC(13)ϪC(14) 104.2(3),
O(2)ϪC(13)ϪC(16) 110.8(4), C(15)ϪC(13)ϪC(16) 110.2.
Figure 1 General structural types of [LiϩXϪ]n (X ϭ halide, OR,
NR2; R ϭ alkyl, aryl).
forces the coordination of the four LiϪO units into a ring
The latter was condensed onto the frozen toluene solution
of MesϪLi·OEt2. After stirring for 4 hours at 213 K the
mixture was allowed to slowly reach room temperature. The
resulting light yellow solid product was washed, recrys-
tallized from n-pentane, isolated, and spectroscopically
characterized.
˚
shape, where the average LiϪO bonds are 1.854 A
˚
(1.802Ϫ1.857 A). The OϪLiϪO bond angles are on average
larger than 120° (132.8° (av)) and the LiϪOϪLi bond
angles tend to be smaller on average than 120° (118.4° (av)).
The intramolecular contact of Li(2) to one F atom of each
˚
˚
˚
CF3 group (2.331 A (av), range: 2.123 A to 2.787 A) elon-
˚
gates the corresponding CϪF bond distances by 0.026 A
(av) in comparison to the other CϪF bonds (1.323 A (av)).
˚
Preparation of [LiOC(CF3)2Mes]4[LiF]2 (2): 2 was formed
by the reaction of [LiOC(CF3)2Mes]4 and AlBr3 in n-hexane
at 273 K. In an poorly understood sequence an F-atom
from the alkoxide is removed rather than that AlBr3 reacts
by metathesis to the lithium alkoxy aluminate Li[Al(ORF)4]
(RF ϭ C(CF3)2Mes). In the course of the decomposition
the [LiF]2 (2) complex was formed (Eq. (2)).
The lithium alkoxide 1 crystallizes in the rare structural
type III; the central structural element is a puckered eight
membered (LiϪO)4 ring (Fig. 2).
Thin, plate-shaped colorless crystals of [LiOC(CF3)2-
Mes]4 (1) (Fig. 2) were obtained by crystallization of a
n-pentane solution at 253 K. The centrosymmetric eight-
membered ring consists of an alternating arrangement of Li
and O atoms, where two of the four electrophilic and small
Li atoms are six-coordinated (LiO2F4 2ϩ4 coordination)
and the other two approach a linear arrangement with some
˚
weak residual LiϪMes interactions (LiϪC: 2.597Ϫ2.791 A;
˚
2.703 A(av)). The tetrameric structure of this lithium or-
ganyl is untypical, since such lithium alkoxides tend to crys-
tallize in the heterocubane (LiOR)4 structure of type V.
Probably the steric demand of the mesitylene residues
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Z. Anorg. Allg. Chem. 2008, 1035Ϫ1040

The Fluorinated Lithiumalkoxide LiORF
Further routes to Li[Al(ORF)4] (RF ϭ C(CF3)2Mes) were
investigated: The reaction in toluene led to an impure and
decomposed non assignable red product mixture. Several
attempts with various conditions (order of adding the pro-
ducts, temperature, solvents) did not lead to the desired pro-
duct Li[Al(ORF)4] and the only clear result was formation
of 2. Thin, plate-shaped colorless crystals of centrosym-
metric [LiOC(CF3)2Mes]4[LiF]2 (2) (Fig. 3) were obtained
by crystallization from n-hexane solution at 253 K.
intramolecular LiϪF contact (1.979 A and 1.982 A).
˚
˚
Several weak residual LiϪMes interactions saturate the six
˚
times
coordinated
Li(1)
(LiϪC:
3.273Ϫ3.340 A
˚
(3.307 A(av)) and the seven times coordinated Li(2) and
˚
˚
Li(3) (LiϪC: 2.837Ϫ3.178 A (2.949 A(av)). The numerous
LiϪF contacts are in very good agreement with other
known structures of fluorinated lithium [1] and the homolo-
gous sodium alkoxides [16Ϫ18] In the comparable heterocu-
bane structure of (LiORЈ)4 (RЈ ϭ C(CF3)3) [10] the ana-
˚
logous LiϪF contacts are longer and at 2.42 A (av) [10].
Preparation of HOC(CF3)2Mes. The general idea of the
preparation of the alcohol HOC(CF3)2Mes was to achieve
the synthesis of the lithium alkoxyaluminate Li[Al(ORF)4]
(RF ϭ C(CF3)2Mes) by reaction with LiAlH4 in analogy to
published procedures [11, 13]. The alcohol was formed by
the acidic hydrolysis (2M HCl) of the fluorinated lithium
alkoxide LiOC(CF3)2Mes under normal atmospheric con-
ditions. The alcohol was separated from the aqueous phase
by extraction with fluorobenzene. Then the alcohol was dis-
tilled, (b.p. ϭ 393 K, 0.01 mbar, inert conditions), dried and
isolated as a colorless liquid (yield: 28 %).
Figure 3 Molecular structure of [LiOC(CF3)2Mes]4[LiF]2 (2) at
140 K with thermal displacement ellipsoids showing 50 % probabi-
lity.
˚
Selected bond lengths and interactions are given in A and angles in °:
Li(1)ϪF(13)Ј 1.940(9), Li(1)ϪF(13) 1.947(9), Li(1)ϪO(1) 1.974(9),
Li(1)ϪO(2) 1.998(9), Li(1)ϪC(24) 3.273, Li(1)ϪC(12) 3.340, Li(2)ϪC(24)
2.837, Li(2)ϪC(12) 2.809, Li(2)ϪC(1) 3.133, Li(2)ϪC(13), Li(3) ϪC(14)
2.845, Li(3)ϪC(1) 2.894, Li(2)ϪF(13) 1.841(9), Li(2)ϪO(1) 1.919(10),
Li(2)ϪO(2)Ј 1.928(10), Li(3)ϪF(13) 1.843(9), Li(3)ϪO(1)Ј 1.976(10),
Li(3)ϪF(5)Ј 1.979(9), Li(3)ϪF(9) 1.982(9), Li(3)ϪO(2) 1.986(9),
F(13)ϪLi(1)Ј 1.940(9), O(1)ϪC(1) 1.392(6), O(1)ϪLi(3)Ј 1.976(10),
O(2)ϪC(13) 1.373(6), O(2)ϪLi(2)Ј 1.928(10), C(1)ϪC(2) 1.549(7),
C(1)ϪC(3) 1.568(7), C(1)ϪC(4) 1.572(7); F(13)ЈϪLi(1)ϪF(13) 86.6(4),
F(13)ЈϪLi(1)ϪO(1) 93.4(4), F(13)ϪLi(1)ϪO(1) 90.3(4), F(13)ЈϪLi(1)ϪO(2)
90.7(4), F(13) ϪLi(1)ϪO(2) 92.4(3), O(1)ϪLi(1)ϪO(2) 175.1(5),
F(13)ϪLi(2)ϪO(1) 95.4(4), F(13)ϪLi(2)ϪO(2)Ј 96.1(4), O(1)ϪLi(2)ϪO(2)Ј
102.2(4), F(13)ϪLi(3)ϪO(1)Ј 96.5(4), F(13)ϪLi(3)ϪF(5)Ј 106.9(4),
O(1)ЈϪLi(3)ϪF(5)Ј 79.0(4), F(13)ϪLi(3)ϪF(9) 112.9(5), O(1)ЈϪLi(3)ϪF(9)
The spectroscopic analyses of HOϪC(CF3)2Mes are as
expected. Moreover, a cyclovoltammogram of the alcohol
in the solvent mixture PC:EC:DMC:toluene ϭ 20:20:50:10
in 1M LiPF6 was recorded. It was observed that, even at
very low potentials, during reduction no evolution of hydro-
gen occurred. This unusual behavior was ascribed to the
bulkiness of RF and is in agreement with the inertness
towards reaction with LiAlH4. Accordingly, the proposed
synthesis of Li[Al(ORF)4] (Eq. 4) did not lead to success,
no reaction could be observed.
150.6(5),
O(1)ЈϪLi(3)ϪO(2) 98.1 (4), F(5)ЈϪLi(3)ϪO(2) 157.1(5), F(9)ϪLi(3)ϪO(2)
78.5(3), Li(1)ЈϪF(13)ϪLi(1) 93.4(4), Li(2)ЈϪO(2)ϪLi(3) 79.0(4),
Li(2)ЈϪO(2)ϪLi(1) 84.4(4), Li(3)ϪO(2)ϪLi(1) 83.0(4), O(1)Ϫ(1)ϪC(2)
107.8(4), O(1)ϪC(1)ϪC(3) 104.1(4), C(2)ϪC(1)ϪC(3) 107.8(4),
F(5)ЈϪLi(3)ϪF(9)
92.8(3),
F(13)ϪLi(3)ϪO(2)
96.0(4),
O(1)ϪC(1)ϪC(4) 111.9(4), C(2)ϪC(1)ϪC(4) 110.7(4), C(3)ϪC(1)ϪC(4)
114.1(4), O(2)ϪC(13)ϪC(16) 111.9(4), O(2)ϪC(13)ϪC(14) 103.9(4),
C(16)ϪC(13)ϪC(14) 115.0(4).
The asymmetric unit consists of two lithium alkoxy- and
one lithium fluoride formula units, where the twelve LiϪO
bonds and eight LiϪF bonds of the symmetry generated
complete molecule form an almost ideal double heterocu-
˚
bane with an average LiϪO bond distance of 1.964 A
˚
(1.919Ϫ1.986 A) and two short Li-F distances at 1.841 and
˚
˚
1.843 A as well as two longer at 1.940 and 1.947 A. The
OϪLiϪO angles of each cube are larger (98.1Ϫ102.2°,
100.2° av) than the LiϪOϪLi angles (79.0Ϫ84.4°, 82.1° av).
Also the O(1)ϪLi(1)ϪO(2) angle of 175.1° along the center-
line proves the slight distortion of this double cage. The two
central cubes are each shielded by two C(CF3)2Mes groups,
where one F atom of every second CF3 group forms an
Z. Anorg. Allg. Chem. 2008, 1035Ϫ1040
© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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1037

L. O. Müller, R. Scopelitti, I. Krossing
Further attempts to prepare Li[Al(ORF)4] were also done
in Et2O with dissolved LiAlH4, but no reaction was ob-
served. Overall, it appears that the novel RF residue is too
bulky to coordinate four times to the (smaller) aluminum
atom. Even coordinating solvents like Et2O did not support
to the formation of Li[Al(ORF)4] from LiAlH4 and 4
RFϪOH.
The slightly distorted square exhibits an OϪGaϪO angle
that is larger (85.07°) than the OϪLiϪO angle (79.5°). Both
are smaller than the LiϪOϪGa angle (97.72°). The two re-
maining free coordination sites of the sixfold coordinated
Li and eightfold coordinated Ga atoms are occupied by a
C2H4Cl2 molecule (coordinated via the Cl atoms), two Br
˚
atoms and two weak LiϪC contacts (LiϪC: 2.945 A) as
˚
well as four weak GaϪF contacts (Ga-F: 3.139-3.189 A
˚
(3.164 A(av)). The C-Cl bond lengths in the coordinated
Preparation of Li(C2H4Cl2)[Ga(OC(CF3)2Mes)2(Br)2] (3). It
was tried to synthesize the analogous lithium alkoxygallate
as in equation 2, but replacing AlBr3 for GaBr3. Gallium is
a bit larger than aluminum and a somewhat weaker Lewis
acid, so it was hoped to overcome the fluoride abstraction
as found by reaction with AlBr3. However, the synthesis
only led to the mixed bromo-alkoxy-gallate 3. Although flu-
oride abstraction did not occur, it appears that the ORF
residue is also too bulky for Gallium to form the tetrasub-
stituted [Ga(ORF)4]Ϫ structure. Colorless crystals of
Li(C2H4Cl2)[Ga(OC(CF3)2Mes)2(Br)2] (3) (Fig. 4) were ob-
tained by crystallization from a dichloroethane solution at
253 K in good yield. The solid-state structure contains half
a molecule in the asymmetric unit. The central structural
feature of 3 is a centrosymmetric, almost square planar Li-
O2Ga ring, which contains a lithium atom that is addition-
ally coordinated by one solvent molecule dichloroethane.
˚
C2H4Cl2 molecule are with 1.781 A similar to the distance
˚
of 1.791 in free C2H4Cl2 [19]. The GaϪBr (2.309 A) and
the GaϪO distances are similar and in good agreement to
ϩ
the GaϪBr bond lengths in [GaBr4]ϪPh2PPPh3 [20]
˚
˚
(2.322 A av) and to the GaϪO distances (1.883 A) in
˚
[Ga(μϪOCMe2Et)(OCMe2ϪEt)2]2 (ϭA) (1.811 A av) [21]
This also fits to the (LiϪOϪGaϪO) ring in
[Li(THF)2][GaN(SiMe3)2(OSiMe3)2Cl] (ϭB), where the the
˚
˚
LiϪO (1.983 A) and GaϪO (1.872 A) bond lengths are
nearly equivalent [22]. In 3 it appears that the small and
hard Liϩ cation coordinates more readily to the harder
O-atoms (and not to the softer and much more accessible
Br-atoms).
˚
The LiϪO distance is 1.995 A, the GaϪO distance is
˚
1.883 A.
Figure 5 Structures of [Ga(μϪOCMe2Et)(OCMe2ϪEt)2]2 (ϭA)
[21] and [Li(THF)2][GaN(SiMe3)2(OSiMe3)2Cl] (ϭB) [22] compa-
red to 3.
Conclusion
The complete structural characterizations of [LiOC-
(CF3)2Mes]4 (1), [LiOC(CF3)2Mes]4[LiF]2 (2) and
Li(C2H4Cl2)[Ga(OC(CF3)2Mes)2(Br)2] (3) were achieved. 1
could be prepared in large scale and with excellent yields;
it is a rare example of a Li-alkoxide that does not adopt a
heterocubane structure. As a side reaction with AlBr3, the
LiF-complex 2 with a double heterocubane structure
formed. The alkoxide could be readily hydrolyzed to the
respective bulky alcohol, which did not react with LiAlH4
and did not liberate H2 upon electrochemical reduction. All
attempts to synthesize WCAs from these starting materials
failed: reactions to prepare Li[Al(ORF)4] from AlBr3 or Li-
AlH4 did not lead to success. Apparently the bulk of the
C(CF3)2Mes residue is to large to allow incorporation to
the desired aluminate. Similarly, the respective [Ga(ORF)4]Ϫ
could not be prepared and only the disubstituted dichloro-
ethanecomplex 3 could be isolated. According to a search
in the CSD database, the latter is the first account of a
Li-Chloroalkane complex. Complex 3 shows that the hard
Liϩ cation prefers coordination of the hard but poorly
accessible oxygen atom over the soft but easily accessible
bromine atoms.
Figure
4
Molecular structure of Li(C2H4Cl2)[Ga(OC(CF3)2-
Mes)2(Br)2] (3) at 140 K with thermal displacement ellipsoids sho-
wing 50 % probability.
˚
Selected bond lengths and interactions are given in A and angles in °:
Li(1)ϪO(1) 1.991(5), Br(1)ϪGa(1) 2.3088(4), Ga(1)ϪO(1) 1.8832(17),
Cl(1)ϪC(13) 1.782(3), Cl(1)ϪLi(1) 2.641(5), Li(1)ϪC(12) 2.945, Ga(1)ϪF(2)
3.189, Ga(1)ϪF(5) 3.139, O(1)ϪC(1) 1.406(3); O(1)ЈϪGa(1)ϪO(1)
85.07(11), O(1)ЈϪGa(1)ϪBr(1)Ј 113.23(5), O(1)ϪGa(1)ϪBr(1)Ј 118.48(5),
Br(1)ЈϪGa(1)ϪBr(1)
Ga(1)ϪO(1)ϪLi(1) 97.72(14), O(1)ϪLi(1)ϪO(1)Ј 79.5(3), O(1)ϪLi(1)ϪCl(1)
110.30(6), O(1)ЈϪLi(1)ϪCl(1) 149.05(6), Cl(1)ϪLi(1)ϪCl(1)Ј 76.88(18),
C(1)ϪO(1)ϪLi(1)
O(1)ϪLi(1)ϪGa(1) 39.74(13).
107.52(2),
C(13)ϪCl(1)ϪLi(1)
105.67(14),
125.1(2),
O(1)ЈϪGa(1)ϪLi(1)
42.54(5),
1038
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Z. Anorg. Allg. Chem. 2008, 1035Ϫ1040

The Fluorinated Lithiumalkoxide LiORF
mately 30 ml n-hexane was given to the powder at 273 K. Only half
of the lithium alkoxide was soluble in the solvent. Afterwards
0.90 g (3.378 mmol) AlBr3 was given at once to the mixture,
whereby it turned dark red. It was refluxed for two hours and then
the dark solid decanted from the colorless solution, which was
isolated, concentrated and crystallized at 253 K. The precipitated
crystals were spectrocopically and structurally assigned to
[LiOC(CF3)2Mes]4[LiF]2 (yieldcrystals: 0.871 g, 21 %). 1H NMR
(400 MHz, [D8]toluene, 298 K) δ ϭ 1.89 (3H, ϪCH3 (ortho)), 2.26
(s, 3H, CH3 (para)), 2.34 (s, 3H, CH3 (ortho)), 6.51 (s, 1H), 6.58
(s, 1H); 19F NMR (376 MHz, [D8]toluene, 298 K) δ ϭ Ϫ73.4 (s,
24F, 4x ϪCF3) (a signal for LiϪF could not be detected), 7Li NMR
(156 MHz, [D8]toluene, 298 K) Ϫ2.1 (s, br., 6Li); IR (CsI plates,
Nujol, 298 K)/cmϪ1: ν ϭ 473 w, 538 w, 589 w, 616 w, 670 w, 708 m,
720 m, 741 m, 750 m, 850 m, 897 s, 930 m, 953 s, 1038 m, 1097 m,
1128 m, 1158 m, 1198 s, 1236 s, 1263 s, 1284 m, sh., 1329 m, sh.,
1377 vs, 1461 vvs, 2975 w.
Experimental Section
General Procedures: Due to the air- and moisture-sensitivity of
most materials all manipulations were undertaken using standard
vacuum and Schlenk techniques as well as in a glove box with a
argon atmosphere (H2O and O2 <1 ppm). All solvents were dried
by conventional drying agents, distilled and stored under argon.
Solution NMR spectra for substance 1 and 2 were recorded in
[D8]toluene, for substance 3 in CDCl3 at room temperature on a
Bruker 400 MHz spectrometer; data are given in ppm relative to
the residual internal solvent signals (1H, 13C) or external FCCl3
(19F). IR spectra of substance 1, 2 and 3 were obtained in Nujol
mulls between CsI plates on a Bruker Vertex 70 IR spectrometer,
Raman spectra were recorded on a Bruker RAM II Raman module
using a highly sensitive Ge detector.
Synthesis of [LiOC(CF3)2Mes]4 (1). In a 500 ml two necked round
bottom flask connected to a dropping funnel and a gas cooler 30 g
(0.150 mol) colorless MesϪLi·OEt2 were dissolved in approxi-
mately 80 ml of toluene. Then 32.37 g (0.195 mol, 1.3 eq., excess)
(CF3)2CO were condensed onto the frozen solution at 77 K. The
mixture was allowed to reach 213 K, whereby the gas cooler was
set with a cryostat to a temperature of 203 K. After stirring for 4
hours at 213 K the mixture was allowed to reach room temperature.
Then the overlaying solution was decanted from the light yellow
solid product. This was isolated, washed with pentane, recrys-
tallized from toluene at 253 K, isolated and dried by vacuum
distillation. The resulting colorless product (yield: 43.10 g, 98 %)
was assigned by X-ray diffraction and spectroscopy as
[LiOC(CF3)2Mes]4.
1H NMR (400 MHz, [D8]toluene, 298 K) δ ϭ 1.74 (s, 3H, ϪCH3 (ortho)),
2.29 (s, 3H, ϪCH3 (para)), 2.50 (s, 3H, ϪCH3 (ortho)), 6.44 (s, 1H), 6.51 (s,
1H); 19F NMR (376 MHz, [D8]toluene, 298 K) δ ϭ Ϫ68.0 (s, 6F, 2x ϪCF3);
7Li NMR (156 MHz, [D8]toluene, 298 K) Ϫ7.9 (s, 1Li); IR (CsI plates, Nujol,
298 K)/cmϪ1: ν ϭ 668 s, 678 w, 711 s, 743 w, 747 w, 851 m, 858 w, 898 s, 931 s,
951 vs, 968 m, 1041 m, 1100 s, 1119 s, 1142 vs, 1156 vs, 1175 s, 1196 s, 1205 s,
1224 vs, 1265 s, 1286 s, 1362 m, 1375 m, 1387 m, 1395 m, 1419 m, 1436 m,
1457 m, 1465 m, 1473 m, 1489 m, 1497 m, 1507 m, 1521 m, 1540 s, 1559 s,
1570 m, 1576 m, 1616 m, 1624 m, 647 m, 1653 s, 1663 m, 1670 m, 1684 m,
1700 m, 1717 m, 1734 m, 1740 m, sh., 1751 m, 1772 m, 1792 m, 2964 s; Ra-
man (298 K)/cmϪ1: 521 (33), 541 (55), 572 (62), 595 (29), 748 (64), 975 (19),
1103 (31), 1170 (16), 1282 (24), 1376 (36), 1385 (40), 1445 (19), 1465 (19),
1566 (14), 1613 (43), 2868 (27), 2923 (100), 2982 (52), 2995 (45), 3009 (36),
3022 (43) [(%)].
Synthesis of Li(C2H4Cl2)[Ga(OC(CF3)2Mes)2(Br)2] (3). In a 250 ml
two necked round bottom flask connected to a dropping funnel
0.40 g (1.283 mmol) GaBr3 dissolved in approximately 1 ml toluene
and were added to a solution of 1.50 g (5.134 mmol) LiO(CF3)2Mes
in approximately 15 ml toluene at 213 K. Then the mixture was
slowly warmed up to room temperature over night. The solution
was decanted from the precipitate (probably LiBr: 0.10 g,
1.151 mmol), concentrated and crystallized from C2H4Cl2 at 253 K.
The resulting crystals were spectroscopically and structurally
assigned as Li(1,2Cl2C2H4)[(Mes(CF3)2CO)2GaBr2] (yieldcrystals
0.72 g, 46 %).
:
1H NMR (400 MHz, CDCl3, 298 K): δ ϭ 2.22 (s, 6H, 2x MesϪCH3), 2.40
(s, 6H, 2x MesϪCH3), 2.60 (s, 2H, ϪCH2CH3), 2.71 (s, 3H, ϪCH2CH3),
3.37 (s, 2H, H2O (trace)), 3.72 (s, 6H, 2x MesϪCH3), 6.91 (s, 2H, MesϪH);
19F NMR (377 MHz, CDCl3, 298 K) δ ϭ Ϫ69.5 (s, 12F, 2x ϪC(CF3)2Mes;
7Li NMR (156 MHz, 298 K) δ ϭ Ϫ3.2 (s, 1Li); IR (CsI plates, Nujol)/cmϪ1
:
ν ϭ 417 w, 485 w, 498 w, 536 m, 543 m, 581 m, 597 w, 645 w, 660 w 679 m,
702 s 714 s, 745 m, 755 m, 867 s, 903 s, 935 s, 959 s, 976 w, sh., 1038 m,
1087 vs, 1130 vs, 1200 vs, 1217 vs, 1238 vs, 1251 vs, 1381 w, 1429 w, 1485 m,
1497 s, 1569 w, 1613 s, 2973 s; Raman (298 K)/cmϪ1: ν ϭ 174 (100), 191 (96),
218 (35), 229 (29), 240 (sh., 19), 283 (31), 325 (23), 315 (19), 336 (18), 347
(12), 377 (9), 400 (12), 411 (10), 545 (30), 555 (30), 575 (24), 598 (13), 649
(13), 662 (18), 703 (10), 722 (5), 755 (19), 763 (20), 980 (16), 1108 (12), 1137
(7), 1148 (12), 1210 (11), 1287 (13), 1383 (24), 1433 (9), 1470 (20), 1573 (8),
1616 (32), 2741 (5), 2761 (5), 2925 (60), 2960 (79), 2999 (40), 3008 (38), 3047
(36) [(%)].
Synthesis of HOC(CF3)2Mes. For the hydrolysis (no inert con-
ditions) of 10 g (34.23 mmol) LiOC(CF3)2Mes, approximately
20 ml of 2M HCl were given to the salt. Then the mixture was
stirred for half an hour and afterwards the resulting alcohol sepa-
rated from the aqueous phase by adding three times about 40 ml
fluorobenzene to the liquid. The organic phase turned light yellow
and was then dried for three hours over about 50 g CaCl2. After
filtration and distillation (bp. of HOC(CF3)2Mes: 393 K,
0.1 mbar), drying over P2O5 and condensation, the alcohol
HOC(CF3)2Mes was isolated as a colourless liquid (yield: 2.70 g,
28 %) and then spectroscopically analyzed.
1H NMR (400 MHz, [D8]toluene, 298 K) δ ϭ 2.07 (3H, ϪCH3 (ortho)), 2.47
(s, 3H, ϪCH3 (para)), 2.64 (s, 3H, ϪCH3 (ortho)), 2.77 (s, 1H OϪH), 6.68
(s, 1H), 6.78 (s, 1H); 19F NMR (376 MHz, [D8]toluene, 298 K) δ ϭ Ϫ77.3 (s,
6F, 2x ϪCF3); IR (CsI plates, nujol, 298 K)/cmϪ1: ν ϭ 485 w, 513 w, 548 w,
590 w, 635 w, 707 s, 741 m, 752 m, 853 m, 890 s, 926 m, 955 s, 983 m, sh.,
1098 m, 1127 vs, 1169 m, 1198 vs, 1238 vs, 1386 w, 1459 m, 1486 m, 1570 w,
1613 m, 2929 w, 3537 m, 3610 m.
X-ray Structure Determination
Crystals of 1, 2 and 3 were obtained as described above. Data were
collected on a Bruker Kappa Apex II diffractometer using Mo-Kα
˚
radiation (λ ϭ 0.71073 A) at T ϭ 140 K and 100 K. Single crystals
were mounted in perfluoroetheroil on top of a glass fiber and then
placed in the cold stream of a low-temperature device so that the
oil solidified. Unit-cell parameters were calculated from a least-
squares refinement of the setting angles of 5000 reflections col-
lected. The space groups were identified as Pbcn (1), P21/c (2) and
P41212 (3). The structure were solved with direct methods in
SHELXS [23] and successive interpretation of the difference
Fourier maps using SHELXL-97. Refinement against F2 was car-
ried out with SHELXL-97. All non-hydrogen atoms were included
anisotropically into the refinement; all hydrogen atoms were in-
cluded isotropically at the calculated positions based on a riding
model. Crystal structure determination of [LiOC(CF3)2Mes]4 (1):
T ϭ 140(2) K, Lorentz polarization correction, monoclinic, Pbcn,
Synthesis of [LiOC(CF3)2Mes]4[LiF]2 (2). 3.947 g (13.510 mmol) of
[LiOC(CF3)2Mes]4 were given into a 250 ml round bottom flask,
connected to a dropping funnel. Then, under stirring, approxi-
˚
˚
Z ϭ 4, a ϭ 11.1781(8) A, b ϭ 15.3994(7) A, c ϭ 28.4597(13), α ϭ
90°, β ϭ 90°, γ ϭ 90°, V ϭ 4898.9(5) A , μ ϭ 0.160 mmϪ1, ρcalc
ϭ
3
˚
Z. Anorg. Allg. Chem. 2008, 1035Ϫ1040
© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.zaac.wiley-vch.de
1039

L. O. Müller, R. Scopelitti, I. Krossing
[3b] A. E. H. Wheatley, Royal Soc. Chem. 2001, 265.
1.584 Mg/m3, θmax ϭ 25.03°, reflections: 28669 collected, 4216
unique (Rint ϭ 0.1289), R1 ϭ 8.35 %, wR2(all data) ϭ 0.2178,
GOF ϭ 1.124. [LiOC(CF3)2Mes]4[LiF]2 (2): T ϭ 140(2) K, Lorentz
polarizationand numerical absorption corrections Tmin/Tmax ϭ
[3c] G. B. Deacon, C. M. Forsyth, N. M. Scott, Dalton Trans.
2001, 2494.
[3d] S. R. Boss, R. Haigh, D. J. Linton, P. Schooler, G. P. Shields,
A. E. H. Wheatley, Daton Trans. 2001, 1001.
[3e] M. Tombul, R. J. Errington, R. A. Coxall, W. Clegg, Acta
Crystallogr. Sect. E. 2003, m137.
˚
0.35396/1.00000, orthorhombic, P21/c, Z ϭ 2, a ϭ 14.7855(10) A,
˚
b ϭ 11.8441(7) A, c ϭ 14.6062(10), α ϭ 90°, β ϭ 99.535(7)°, γ ϭ
3
90°, V ϭ 2522.5(3) A , μ ϭ 0.163 mmϪ1, ρcalc ϭ 1.607 Mg/m3,
˚
[3f] M. Tombul, R. J. Errington, R. A. Coxall, W. Clegg, Acta
θmax ϭ 25.03°, reflections: 15376 collected, 4371 unique (Rint
ϭ
Crystallogr. Sect. E. 2003, m231.
[4] E. Weiss, Angew. Chem. 1993, 105, 1565; Angew. Chem. Int.
Ed. Engl. 1993, 32, 1501.
[5] A. Reisinger, D. Himmel, I. Krossing, Angew Chem. 2006, 118,
7153; Angew Chem. Int. Ed. Engl. 2006, 45, 6997.
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26, 2096.
0.1144) R1 ϭ 7.05 %, wR2(all data) ϭ 0.1994, GOF ϭ 1.053.
Li(C2H4Cl2)[Ga(OC(CF3)2Mes)2(Br)2] (3): T ϭ 100(2) K, Lorentz
polarization and numerical absorption corrections Tmin/Tmax ϭ
˚
0.65857/1.00000, tetragonal, P41212, Z ϭ 4, a ϭ 11.1582(10) A, b ϭ
˚
11.1582(10) A, c ϭ 26.1495(16), α ϭ 90°, β ϭ 90°, γ ϭ 90°, V ϭ
3
3255.8(5) A , μ ϭ 3.558 mmϪ1, ρcalc ϭ 1.848 Mg/m3, 2θmax
ϭ
˚
27.51°, reflections: 125178 collected, 3741 unique (Rint ϭ 0.0572)
R1 ϭ 2.90 %, wR2(all data) ϭ 0.0559, GOF ϭ 1.213, the refined
Flack parameter equals to 0.078(8). Crystallographic data for the
structures have been deposited with the Cambridge Crystallo-
graphic Data Centre: CCDC 655228 (2), 655229 (1), 655230 (3).
Copies of the data can be obtained free of charge on application
to The Director, CCDC, 12 Union Road, Cambridge CB2,
1EZ, UK (Fax: int.codeϩ(1223)336-033; e-mail for inquiry:
fileserv@ccdc.cam.ac.uk; e-mail for deposition: deposit@
ccdc.cam.ac.uk)
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Eaton, J. Michl, Org. Lett. 2001, 3, 2375.
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1993, 115, 5093.
Acknowledgement. This work was supported by the EPF Lausanne,
the Albert-Ludwigs-Universität Freiburg, the Deutsche Forschungs-
gemeinschaft, the Schweizer Nationalfonds, the Fonds der Chem-
ischen Industrie and BASF in Ludwigshafen.
[13] R. E. A. Dear, W. B. Fox, R. J. Fredericks, E. E. Gilbert, D.
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76th edition, 1995؊1996.
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1040
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© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Z. Anorg. Allg. Chem. 2008, 1035Ϫ1040